It is known that a polymer having at least one reactive silicon group in its molecule has a nature that the polymer is crosslinked through formation of siloxane bonds, which follows hydrolysis reaction or the like of the reactive silicon group due to moisture or the like, even at room temperature, so as to give a rubbery cured product.
Out of such polymers having a reactive silicon group, polymers having a main chain skeleton made of polyoxyalkylene based polymer or polyisobutylene based polymer are disclosed in JP-A-52-73998, JP-A-63-6041 and the like, and have already been industrially produced and have widely been used for sealants, adhesives, paints and the like.
Curable compositions containing a polymer having a main chain skeleton made of polysiloxane, in particular, diorganopolysiloxane have also been reported in many documents such as JP-A-55-43119.
Curable compositions used for sealants, adhesives, paints and the like, and rubbery cured products obtained by curing the compositions are required to have various properties such as curability, adhesiveness, and mechanical properties.
A curable catalyst has been used for curing a curable composition containing a polymer having a reactive silicon group. Usually, an organotin catalyst having a carbon-tin bond, such as dibutyltin bis(acetylacetonate) has widely been used. In recent years, however, about organotin compounds, the toxicity thereof has been pointed out. Thus, organotin-free catalysts have been desired to be developed.
Many researches have been made on metal carboxylates, metal alkoxides, and the like as organotin-free catalysts. Among them, carboxylic acids or amine compounds are catalysts containing no metal, and are expected to give only relatively small effects onto the environment. JP-A-05-117519 discloses that use of a combination of a carboxylic acid with an amine gives a curable composition having a good curability. However, in curable compositions which are cured by a silanol condensation catalyst in which an amine compound and a carboxylic acid are used in combination, there remains room for improvement to gain a sufficient adhesiveness suitable for applications such as sealants, adhesives and the like. Moreover, as stated in JP-A-05-117519, sufficient curability is not easily obtained by use of an amine compound alone.
JP-A-2001-207070 discloses that a curable composition wherein a compound having a fluorine anion is used as a catalyst has an excellent curability and the cured product obtained therefrom has an excellent adhesive property.
In many cases, a filler is added to a curable composition used for sealants, adhesives, paints or the like, or a rubbery cured product obtained by curing the composition in order to improve the strength, improve the workability, give designability, or attain some other purpose; however, in the case of using a fluoride salt compound as a curing catalyst for an organic polymer having a reactive silicon group, the addition of a filler causes a problem that the curability of the curable composition is deteriorated.
In the meantime, JP-A-2001-207070 illustrates, as a compound having a fluorine anion, a quaternary ammonium fluoride salt, a fluoride salt of an alkali metal, or some other compound.
However, the quaternary ammonium fluoride salt is instable in the state that the fluoride salt is isolated; thus, the fluoride salt is supplied in a solution state that the fluoride salt is dissolved in water or an organic solvent. When an aqueous solution of the quaternary ammonium fluoride salt is used as a catalyst, a curable composition good in storage stability is not easily obtained by effect of water. When the solution of the quaternary ammonium fluoride salt dissolved in an organic solvent is used as a catalyst, a large amount of a volatile component remains easily in the resultant sealants or adhesives by effect of the organic solvent. Thus, a problem is caused against the purpose of putting it into industrially practical use. Additionally, the quaternary ammonium fluoride salt is expensive; from this viewpoint also, a problem remains against the industrially practical use. Furthermore, a fluoride salt of an alkali metal is not generally good in compatibility with any organic compound. Thus, when the fluoride salt is used as a catalyst, there is caused a problem that the fluoride salt does not easily gain curing performance.
As described above, there has not yet been obtained any curable composition wherein a compound having a fluorine anion, which can be put into industrially practical use, is used as a catalyst. Thus, such a composition has been desired to be developed under the present circumstances.